1. Field of Invention
The present invention relates to a current generating circuit, an electro-optical apparatus, and an electronic unit that are suitable for use in driving display panels, for example, organic EL (Electronic Luminescence) panels.
2. Description of Related Art
Organic EL panels are attracting attention as next-generation display panels. The reason for this is that organic EL devices used in organic EL panels are self-light-emitting devices, as opposed to liquid crystal devices used in liquid crystal panels that merely change the amount by which the liquid crystal devices transmit light. The organic EL panels also exhibit excellent characteristics, for example, a wider viewing angle, a higher contrast, and a faster response speed than those of the liquid crystal panels. Unlike the liquid crystal devices, which are voltage-driven devices, the organic EL devices are so-called “current-driven devices.” Accordingly, for driving the organic EL devices, instead of a voltage, a current should be generated in accordance with the grayscale (luminance) level, and thus, a current generating D/A converter has been invented. (See, for example, Japanese Unexamined Patent Application Publication No. 2000-122608.)
It is generally known that the humans' visual characteristics have logarithmic or exponential properties. Even if the grayscale changes linearly, it does not sometimes appear to the humans' eyes that the grayscale changes linearly. In view of these circumstances, it is common that non-linear characteristics (γ characteristics), for example, logarithmic or exponential characteristics, are provided in an electro-optical apparatus so that they appear to be linear characteristics for the humans' eyes. This type of processing is sometimes referred to as γ correction.
The following operation can be considered when taken this γ correction into consideration. A current signal having non-linear characteristics is generated for digital data indicating that the grayscale (luminance) of organic EL devices is linear, and is then provided to the organic EL devices, thereby allowing an observer to visually recognize that the grayscale changes linearly.
As the above type of operation, the following operations, for example, can be considered: (1) digital data having linear characteristics is converted into digital data having non-linear characteristics by using a table; and (2) the grayscale range represented by digital data is divided into a plurality of areas, and in the divided areas, required γ characteristics are approximated by using a plurality of linear characteristics.